The present invention relates to an agent and a method for purifying flue gas and incinerated ash. More particularly, the invention relates to an agent and a method for decomposing or removing toxic components from flue gas or incinerated ash in which toxic substances such as dioxins and nitrogen oxides are contained.
It has so far been reported that various substances generated by combustion cause air pollution and exert bad effects to living things. For example, nitrogen oxide (Nox) is said to be a main culprit in acid rain and photochemical smog, and some respiratory diseases.
In combustion, highly toxic dioxins such as polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are evolved. Such dioxins have now become a serious social problem, since they cause chlorine acne, pigmentation, alopecia, hirsutism, liver disorder, miscarriage, pregnancy abnormalities and thus exert immeasurably harmful effects on humans.
It has thus been desired to devise a new method for removing toxic substances such as dioxins and nitrogen oxides from flue gases and incinerated ashes. Various measures are now being tried in various countries to control the emission of nitrogen oxides and to prevent the generation of dioxins.
An example of a conventional method for purifying flue gas containing nitrogen oxides is a catalytic reduction method using ammonia. However, this method requires an intricate apparatus for safely handling ammonia and is quite costly. In addition, where sulfur oxides are contained in the flue gases, compounds such as ammonium hydrogensulfate and ammonium disulfate, which may be a cause of corrosion, are generated and may affect the apparatus.
Another conventional method is a method for adsorbing nitrogen oxides into active carbon fiber. However, in this method, activated carbon fiber has low adsorptive capacity for nitrogen monoxide, so that complete removal of nitrogen oxides is difficult. Still another conventional method is a method for allowing activated carbon fiber to support metal hydroxides and metal oxides so as to increase adsorptive capacity for nitrogen monoxide. However, since active carbon fiber has a limit of adsorptive capacity and simply adsorbs toxic substances, no fundamental solution is derived from this method.
In order to prevent the generation of dioxins, high-temperature incineration or complete incineration of wastes has been studied. However, the construction cost of a combustion facility entails high cost and the complete prevention of dioxins may often be difficult to achieve.
An object of the present invention is to provide an agent for purifying flue gas and incinerated ash, which does not have any above problems.
As a result of intensive studies to achieve an agent for purifying flue gas and incinerated ash, which has excellent purifying capacities and can be safely disposed of after being used, the inventors have attained the present invention.
An agent for purifying flue gas and incinerated ash according to the present invention contains: one or more kinds of salts selected from alkali metal silicates; fluoride ion; hydrogencarbonate ion; and water-soluble alcohols or derivatives thereof.
In the agent according to the present invention, the one or more salts selected from alkali metal silicates can be sodium silicate.
In the agent according to the present invention, the water soluble alcohols or the derivatives thereof can be ethylene glycol.
In a method for purifying flue gas according to the present invention, any one of the above agents is sprayed to the flue gas.
In a method for purifying incinerated ash according to the present invention, any one of the above agents is sprayed to the fly incineration.